The present invention relates generally to ground collision avoidance system. More specifically, the present invention relates to an adaptive (e.g., scaleable and autonomous regardless of the aircraft type) ground collision avoidance system utilizing numerous sensors and cross checks to provide an accurate ground collision warning while at the same time avoiding unnecessary nuisance warnings.
As is well known in the aviation fields, avoiding controlled flight into the ground or ground collision is a very important endeavor. Every year many lives are lost due to the collision between an aircraft and the ground. Many times ground collision is caused by the pilot having misinformation or becoming disorientated and flying directly into the ground. Furthermore, ground collision is a problem for both military and commercial aircraft alike. Therefore, to promote the safety of air travel, systems that avoid collision with the ground are highly desirable.
In the past numerous systems have been developed to provide such ground collision avoidance. One type of system utilizes aircraft sensors to determine the proximity of the aircraft to the ground. These sensors can include barometric altimeters, radar altimeters, and forward looking infrared radar. While such equipment does provide a warning of the possibility of collision with the ground, these systems are highly limited by the capabilities of the sensors themselves.
A second type of system utilizes a predetermined minimum safe altitude for given region in which the aircraft is traveling. Consequently, if the aircraft travels below this predetermined minimum safe altitude, then a warning indicates to the pilots that they are in danger of ground collision. This system is fine for providing general warnings in a flat terrain environment. However, in certain situations, such as fighter aircraft performing terrain following missions, when an aircraft is required to travel at low altitudes above the ground this system is impractical. This is especially true in geographic regions having large variations in elevation.
Another system for providing ground collision avoidance warnings is one wherein the flight dynamics of an aircraft are constantly monitored to provide an indication of possible collision. More specifically, the altitude loss is monitored during numerous maneuvers and is subsequently interpolated to determine whether ground collision is imminent. This type of system, however, is incapable of predicting the true ground situation and the maneuvering controls or considering maneuvering alternatives available to the pilot. It is well known that while in a dive typically a pilot will eventually pull out. If altitude loss interpolation is carried out at this point then a false warning or nuisance warning will surely sound. For this reason this type of system is also impractical.
One overriding consideration when designing a ground collision avoidance system is the avoidance of constant false warnings or nuisance warnings. Systems can be devised having differing sensitivities and differing warning methodology. However, these systems are of no use to a pilot if they provide continuous nuisance warnings suggesting that the pilot is in imminent danger of ground collision, when in reality the pilot is flying in a safe condition. If too many nuisance warnings are provided, the ground collision avoidance system will likely be disabled and at that point become totally useless. For this reason it is desirable to provide a very realistic system capable of providing ground collision avoidance warnings only at a point when they are likely to be meaningful and heeded by the flight crew.